Merge tag 'kvm-x86-svm-6.8' of https://github.com/kvm-x86/linux into HEAD

KVM SVM changes for 6.8:

- Revert a bogus, made-up nested SVM consistency check for TLB_CONTROL.

- Advertise flush-by-ASID support for nSVM unconditionally, as KVM always
flushes on nested transitions, i.e. always satisfies flush requests. This
allows running bleeding edge versions of VMware Workstation on top of KVM.

- Sanity check that the CPU supports flush-by-ASID when enabling SEV support.

- Fix a benign NMI virtualization bug where KVM would unnecessarily intercept
IRET when manually injecting an NMI, e.g. when KVM pends an NMI and injects
a second, "simultaneous" NMI.

arch/x86/kvm/svm/nested.c

···
 	    kvm_vcpu_is_legal_gpa(vcpu, addr + size - 1);
 }
 
-static bool nested_svm_check_tlb_ctl(struct kvm_vcpu *vcpu, u8 tlb_ctl)
-{
-	/* Nested FLUSHBYASID is not supported yet.  */
-	switch(tlb_ctl) {
-		case TLB_CONTROL_DO_NOTHING:
-		case TLB_CONTROL_FLUSH_ALL_ASID:
-			return true;
-		default:
-			return false;
-	}
-}
-
 static bool __nested_vmcb_check_controls(struct kvm_vcpu *vcpu,
 					 struct vmcb_ctrl_area_cached *control)
 {
···
 		return false;
 	if (CC(!nested_svm_check_bitmap_pa(vcpu, control->iopm_base_pa,
 					   IOPM_SIZE)))
-		return false;
-
-	if (CC(!nested_svm_check_tlb_ctl(vcpu, control->tlb_ctl)))
 		return false;
 
 	if (CC((control->int_ctl & V_NMI_ENABLE_MASK) &&

arch/x86/kvm/svm/sev.c

···
 	/*
 	 * SEV must obviously be supported in hardware.  Sanity check that the
 	 * CPU supports decode assists, which is mandatory for SEV guests to
-	 * support instruction emulation.
+	 * support instruction emulation.  Ditto for flushing by ASID, as SEV
+	 * guests are bound to a single ASID, i.e. KVM can't rotate to a new
+	 * ASID to effect a TLB flush.
 	 */
 	if (!boot_cpu_has(X86_FEATURE_SEV) ||
-	    WARN_ON_ONCE(!boot_cpu_has(X86_FEATURE_DECODEASSISTS)))
+	    WARN_ON_ONCE(!boot_cpu_has(X86_FEATURE_DECODEASSISTS)) ||
+	    WARN_ON_ONCE(!boot_cpu_has(X86_FEATURE_FLUSHBYASID)))
 		goto out;
 
 	/* Retrieve SEV CPUID information */

arch/x86/kvm/svm/svm.c

···
 	if (svm->nmi_l1_to_l2)
 		return;
 
-	svm->nmi_masked = true;
-	svm_set_iret_intercept(svm);
+	/*
+	 * No need to manually track NMI masking when vNMI is enabled, hardware
+	 * automatically sets V_NMI_BLOCKING_MASK as appropriate, including the
+	 * case where software directly injects an NMI.
+	 */
+	if (!is_vnmi_enabled(svm)) {
+		svm->nmi_masked = true;
+		svm_set_iret_intercept(svm);
+	}
 	++vcpu->stat.nmi_injections;
 }
 
···
 	if (nested) {
 		kvm_cpu_cap_set(X86_FEATURE_SVM);
 		kvm_cpu_cap_set(X86_FEATURE_VMCBCLEAN);
+
+		/*
+		 * KVM currently flushes TLBs on *every* nested SVM transition,
+		 * and so for all intents and purposes KVM supports flushing by
+		 * ASID, i.e. KVM is guaranteed to honor every L1 ASID flush.
+		 */
+		kvm_cpu_cap_set(X86_FEATURE_FLUSHBYASID);
 
 		if (nrips)
 			kvm_cpu_cap_set(X86_FEATURE_NRIPS);